Wire scaffold device for ventricular assist device

ABSTRACT

A ventricular assist system includes a ventricular assist device (“VAD”) and an expandable stent. The VAD may include a pump and an inlet element defining an inlet opening communicating with the pump, the inlet element being adapted for positioning with the inlet opening disposed within a ventricle of a heart when the system is in an operative condition. The expandable stent may be adapted for positioning within the ventricle when the system is in the operative condition. The pump may be operated to draw blood from the ventricle and return the blood to the artery, and a wall of the ventricle may be held away from the inlet opening with the stent. The stent may be passed through a channel in the ventricular assist device while the stent is in a collapsed condition.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims the benefit of the filing date of U.S.Provisional Patent Application No. 61/860,074 filed Jul. 30, 2013, thedisclosure of which is hereby incorporated herein by reference.

BACKGROUND

The present disclosure relates to ventricular assist devices (“VADs”),to components useful in such devices, and to methods of using the same.

In certain disease states, the heart lacks sufficient pumping capacityto meet the needs of the body. This inadequacy can be alleviated byproviding a mechanical pumping device, such as a VAD, to supplement thepumping action of the heart. Considerable effort has been devoted toproviding a VAD which can be implanted and which can remain in operationfor months or years to keep the patient alive while the heart heals, orwhich can remain in operation permanently or until a suitable donorheart becomes available if the heart does not heal.

A VAD is typically connected to the heart, most commonly to the leftventricle. For example, a VAD may include a pump which is installed inthe body outside of the heart. The VAD may have an inlet cannulaconnected to the interior of the left ventricle and connected to theintake of the pump. The VAD may also include an outlet tube connectedbetween the outlet of the pump and the aorta. Once connected, the VADand the heart both pump blood from the left ventricle to the aorta. SomeVADs may include a fluid intake or inlet within a chamber of the heart,such within the left ventricle. For example, U.S. Patent Publication No.2009/0203957, the disclosure of which is hereby incorporated byreference herein, discloses a VAD with an inlet positioned within theleft ventricle.

With such systems, depending on the particular positioning of the inlet,the operating parameters of the VAD, and the anatomy of the patient, asituation may arise in which heart tissue is pulled into the pump inlet.For example, a wall of the ventricle, the papillary muscles, or chordaetendinae may be sucked partially into the inlet. In other situations,such as when there is relatively little volume of fluid in the leftventricle, the walls of the left ventricle may be caused to partiallycollapse due to forces caused by the pump. Such a situation may bedescribed as a suction condition. The scenarios described above maycause the pump to malfunction and may cause injury to the patient.

Patients with heart failure may have reduced left ventricular diametersthat reduce the ability of the heart to fill during diastole. Forexample, some patients may have conditions such as hypertrophiccardiomyopathy in which walls of the heart become thick and rigid, ordiastolic dysfunction in which the ventricle does not relax properlyduring diastole. In these patients, the ventricle may not fill with asmuch blood as in a healthy heart. Using existing VADs in patients withthese types of conditions may be difficult.

BRIEF SUMMARY

One aspect of the present disclosure provides a ventricular assistsystem including a VAD and an expandable stent. The VAD may include apump and an inlet element defining an inlet opening communicating withthe pump, the inlet element being adapted for positioning with the inletopening disposed within a ventricle of a heart when the system is in anoperative condition. The expandable stent may be adapted for positioningwithin the ventricle when the system is in the operative condition. Thesystem may also include a mounting that secures a part of the stent inposition relative to the inlet element when the stent is positionedwithin the ventricle. The mounting may include an anchor elementconfigured for attachment to the heart and the inlet element and thestent may be secured to the anchor element with the system is in theoperative condition. The anchor element may include a channel extendingtherethrough. A one-way valve may be positioned at least partiallywithin the channel. The system may include a sealing element configuredto be positioned within the channel proximal to the one-way valve toseal the channel. The channel may have a diameter and the stent may havea collapsed condition and an expanded condition, the diameter of thechannel being adapted to allow the stent to pass through the channelwhen the stent is in the collapsed condition. The anchor element mayinclude a ring. The anchor element may include a substantiallycylindrical member configured to be mounted to the heart at variouspositions along a length of the substantially cylindrical member. Thestent may include a plurality of struts, the struts having inner endsand outer ends, the inner ends being disposed adjacent one another andthe outer ends extending away from one another when the stent is in anexpanded condition. The stent may be substantially cylindrical when inthe expanded condition. The stent may be formed of a braided mesh.

Another aspect of the present disclosure includes a method of installinga ventricular assist device in a subject. The method may includemounting the ventricular assist device to the subject so that an inletopening of an inlet element is disposed within a ventricle of the heartand the inlet opening communicates with a pump. The method may alsoinclude positioning an outflow cannula so that the outflow cannulacommunicates with the pump and with an artery, and positioning a stentin the ventricle at least partially upstream of the inlet of the pump.The pump may be operated to draw blood from the ventricle and return theblood to the artery, and a wall of the ventricle may be held away fromthe inlet opening with the stent. The stent may be passed through achannel in the ventricular assist device while the stent is in acollapsed condition. The step of passing the stent through the channelin the ventricular assist device may include passing the stent through aone-way valve positioned at least partially within the channel. Thestent may be transitioned from the collapsed condition to an expandedcondition. The channel may be sealed with a sealing element.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic perspective view of a ventricular assistdevice.

FIG. 2 is diagrammatic perspective view of the device of FIG. 1 from adifferent perspective.

FIG. 3 is a perspective view of a pump of the device of FIG. 1.

FIG. 4 is a diagrammatic view of the device of FIG. 1 in an installedcondition, in conjunction with the certain structures of the heart.

FIG. 5 is a diagrammatic perspective view of another embodiment of aventricular assist device.

FIG. 6 is a cross-sectional view of the ventricular assist device ofFIG. 5.

FIG. 7 is an enlarged cross-sectional view of a portion of the device ofFIG. 5.

FIG. 8 is a highly schematic view of the device of FIG. 5 in animplanted condition within a heart.

FIG. 9 is an enlarged cross-sectional view of a catheter inserted intothe device of FIG. 5.

FIG. 10 is an enlarged cross-sectional view of a portion of the deviceof FIG. 5 with a stent mounted thereto.

FIG. 11 is a schematic view of the device of FIG. 5 implanted within aheart with a stent mounted to the device.

FIG. 12 is a perspective view of a cylindrical stent in an expandedcondition.

FIG. 13 is a diagrammatic perspective view of another embodiment of aVAD.

FIG. 14 is a diagrammatic perspective view of the VAD of FIG. 13 and thestent of FIG. 12 implanted into a heart.

FIG. 15 is a highly schematic representation of a further embodiment ofa VAD implanted into a heart with a stent positioned within the heart.

DETAILED DESCRIPTION

As used herein, the words “proximal” and “distal” denote directions andends of the device and components. When referring the VAD or componentsthereof, the term “proximal” refers to the direction toward the surgeonor other operating room personnel during installation of the device andthe term “distal” has the opposite meaning. Furthermore, when referringto the VAD or component thereof, the term “upstream” or “inflow” refersto a direction opposite the flow of blood in the VAD when operating asintended, while the term “downstream” or “outflow” refers to a directionwith the flow of blood in the VAD when operating as intended.

Referring to the drawings, wherein like reference numerals refer to likeelements, there is shown in FIGS. 1-2, an embodiment of a VAD 10. VAD 10may include four sections including a pump 20, an outflow cannula 40, arigid elongate member 60, and an anchoring element, such as ring 80.

One embodiment of pump 20 is shown in greater detail in FIG. 3. Pump 20may be an axial flow pump having an inlet element 21 at an upstreamposition and an outlet 23 at a downstream position, the inlet 21 andoutlet 23 arranged along an axis 19 referred to herein as the pump axis.The pump 20 may include an axial bore defined by a tubular housing 22which extends between the inlet 21 and the outlet 22. Housing 22 mayformed from biocompatible materials such as ceramics and metals such astitanium. The materials used for those portions of the housing 22disposed inside the motor stator (discussed below) desirably arenon-magnetic dielectric materials such as ceramics.

A motor stator may be disposed around the outside of tubular housing 22.The motor stator is arranged to provide a rotating magnetic field.Preferably, the motor stator contains both magnetic laminations and wirecoils (not shown). Electrical current may be passed sequentially throughthe wire coils to produce the rotating electromagnetic field. The motorstator may be a conventional slotted or slotless design or may utilizean annular or toroidal design.

A rotor 26 may be disposed within the axial bore in alignment with themotor stator. Rotor 26 may be formed from a unitary piece of amagnetizable, biocompatible platinum-cobalt or platinum-cobalt-boronalloy. The rotor 26 may have a central axis coincident with pump axis19, and may include a plurality of blades 34 projecting outwardly fromsuch axis and curving around the axis in a generally helical patternhaving a pitch angle which varies along the axial length of the rotor26. The blades 34 may define flow channels 36 between them. Blades 34may be configured so that their circumferential surfaces act ashydrodynamic bearings. Multiple hydrodynamic bearing surfaces may beprovided on each blade, spaced along the axial length of the rotor 26,for greater hydrodynamic stability during operation. These rotor blades34 may be magnetized for magnetic coupling to the motor stator. Thenumber of rotor blades 34 is preferably either two or four for symmetryof magnetic poles. The rotor blades 34 impel blood within the housing 22axially, toward the outlet 23.

The features of the rotor 26 and motor stator may be generally as shownin U.S. Patent Publication No. 2009/0112312 (“the '312 Publication”),the disclosure of which is hereby incorporated by reference herein.However, pump 20 typically is larger than a pump intended forpositioning within an artery described in the '312 Publication. As analternative to the unitary magnetic rotor 26 discussed above, aconventional rotor design involving placement of magnets sealed within arotor formed from non-magnetic material may be used.

The pump may also include diffuser blades 28 mounted within housing 22downstream from rotor 26, between the rotor 26 and the outlet 23. Asbest seen in FIG. 3, each diffuser blade 28 may be generally in the formof a plate-like vane secured to the housing 22 and projecting radiallyinto the axial bore from the wall of the housing 22. The upstream endsof the diffuser blades 28, closest to rotor 26, may curve in acircumferential direction around the axis 19. The direction of curvatureof the diffuser blades 28 may be opposite to the direction of curvatureof the rotor blades 26. Preferably, the number of diffuser blades 28 isunequal to the number of rotor blades 34, and the number of diffuserblades 28 is not an integral multiple or divisor of the number of pumpblades. Thus, where the rotor 26 has an even number of blades 34, thepump 20 desirably has an odd number of diffuser blades 28, such as threeor five diffuser blades 28. This arrangement may help to maximize thestability of the rotor 26 and minimize vibration in operation of thepump 20. However, it should be understood that two, four, or more thanfive diffuser blades 28 may be utilized. During operation, the bloodpassing downstream from the rotor 26 has rotational momentum imparted bythe rotor 26. As the blood encounters the diffuser blades 28, thisrotational momentum is converted to axial momentum and pressure head.Thus, the diffuser blades 28 serve to reclaim the energy used to createthe rotational motion and convert that energy to useful pumping work. Inthis embodiment, the diffuser blades 28 are not attached to one anotherat the axis. This arrangement conserves space within the axial bore, andthus maximizes axial flow.

Pump 20 may include an exterior shroud surrounding the housing 22 andmotor stator. The shroud may be formed from a biocompatible metal suchas titanium, a ceramic, or a biocompatible polymer. Exteriorthromboresistant coatings may also be utilized to improvehemocompatibility. The shroud may define a first attachment portion 30at the proximal or upstream end of the housing, near inlet 21. The firstattachment portion 30 (FIG. 2) may have a recessed cavity 38 whichextends into the shroud in a direction parallel to pump axis 19 butoffset from the pump axis.

The apparatus may also include an elongate member 60 which has aproximal end 61, a distal end 63 and a bore 62 therethrough. Preferably,elongate member 60 has an axis along its direction of elongation whichaxis is parallel to the axis 19 of the pump body but offset from axis 19in a direction transverse to both axes. Merely by way of example,elongate member 60 may be a tube formed from titanium or otherbiocompatible metal. Member 60 desirably is substantially rigid. Thatis, the member desirably is rigid enough to maintain the pump 20 inposition, with no substantial movement relative to the ring 80 under theloads normally applied to the system while the system is in place withinthe heart. Elongate member 60 may include a spherical ball 90 mountedalong the length thereof, remote from the distal end 63. Ball 90 may befixedly attached to member 60 as, for example, by welding.

The distal end 63 of member 60 is received in recess 38 of firstattachment portion 30 of the pump 20. Preferably, the distal end ofmember 60 is joined to the attachment portion of the pump by apermanent, fluid-tight connection as, for example, by welding member 60to the pump shroud. Electrical power wiring 67 extends from the motorstator through bore 62 of member 60 and out of the member through afitting 100 at the proximal end of the member. Preferably, there is afluid-tight feedthrough (not shown) at fitting 100, at the connectionbetween the distal end 63 and the attachment portion 30 of the pump 20,or both. The electrical wiring 67 extends out of the fitting 100 to asource of electrical power (not shown) external to the body of thepatient or implanted within the body of the patient.

An outflow cannula 40 of extends distally from a distal end of pump 20in the downstream direction. Outflow cannula 40 may be generally in theform of a hollow tube having a proximal end attached to pump 20 andcommunicating with the outlet 23 of the pump 20. The outflow cannula mayhave a tip 70 at its distal or outflow end.

Preferably, outflow cannula 40 is a single molded polymer piece made ofthermoplastic polyurethanes (segmented and/or copolymerized withsilicone, polycarbonate-urethanes, polyether-urethanes, aliphaticpolycarbonate, or other additives), silicone, polycarbonate-urethanes,polyether-urethanes, aliphatic polycarbonate, silicone material with orwithout catalyst metals and possibly sulfonated styrenic polymers.Preferably, outflow cannula 40 may be cast with or without titanium wirestructures for bend enhancement properties and non-invasivevisualization of a catheter typically under x-ray or fluoroscopy. Theoutflow cannula 40 may contain barium sulfate or other minerals, ormetallic marker bands to provide landmark location visualization byfluoroscopic, CAT or other radiological techniques during or afterimplantation in the patient.

Outflow cannula 40 may be straight or bent and desirably has anappropriate stiffness and hardness to accommodate the native heart andaortic root geometry and also to have non-traumatic contact withtissues. The diameter of the outflow cannula 40 may be tapered from pumphousing 22 to a smaller diameter near the distal end of the outflowcannula 40. The distal end of the outflow cannula 40 may project throughthe aortic valve when the apparatus is implanted in a patient. A cannulawhich tapers in diameter towards its distal end may provide relativelylow flow resistance due to its comparatively large diameter at theproximal end, and may also provide a desirable small diameter portion atthe aortic valve. The small-diameter portion at the aortic valve helpsto minimize aortic valve insufficiency, e.g. retrograde flow through thevalve due to poor sealing of the tri-leaflets around the cannula.Desirably, the outflow cannula 40 is round in cross-section, at least inthe region near tip 70 which may extend through the aortic valve whenimplanted. A round cross-sectional shape also minimizes aortic valveinsufficiency.

The tip 70 of outflow cannula 40 may have any one of various shapes andgeometries. For example, as shown, tip 70 has a circumferential surfacewhich tapers inwardly toward the axis of the outflow cannula 40 in thedistal direction, and thus converges toward the distal extremity of theoutflow cannula 40. The distal surface of the tip 70 may define asmooth, dome-like shape at the distal extremity of the tip 70. Aplurality of openings may extend through the circumferential surface ofthe tip 70 and communicate with the interior bore of the outflow cannula40. When blood is discharged through these openings, the flow has aradial component which may provide a hydrodynamic self-centering forcefor cannula 40. The centering action may further minimize aortic valveinsufficiency. Moreover, even if the cannula tip 70 is resting againstan arterial wall, the plural openings spaced around the circumference ofthe tip 70 will still provide good blood flow. This tip geometry andother tip geometries are described in more detail in U.S. PatentPublication Nos. 2009/0203957 and 2010/0022939, the disclosures of whichare both hereby incorporated by reference herein.

In this embodiment, the device 10 also includes an anchoring element inthe form of a ring 80. Preferably, ring 80 is adapted for mountingadjacent the apex of the patient's heart by sewing around a perimeter ofring 80 to tissue along a wall of the patient's heart. For example, ring80 may be a metallic structure having a peripheral flange with numerousholes for sewing or stapling the ring to the heart wall. The peripheryof ring 80 may be covered with a fabric material such as for examplepolyester material, expanded polytetrafluoroethylene, felt or the likefor promoting tissue growth over the ring to further secure the ring inplace. U.S. Patent Publication No. 2007/0134993 describes ringcomponents in more detail and is herein incorporated by referenceherein.

Ring 80 preferably includes a spherical socket adapted to engage thespherical ball 90 of elongate member 60 such that ring 80 is pivotallyor polyaxially mounted to elongate member 60 remote from pump 20. In theembodiment depicted, the pivotable connection between the ring 80 andthe ball may be a permanent connection formed during manufacture. Forexample, ball 90 may be entrapped between elements of the ring 80 whichare permanently connected to one another during manufacture. Ring 80 maybe configured to align to the heart wall but can also allow forrotational movement to accommodate the native heart movement.

In a method of implantation, the VAD 10, including the ring 80, member60, pump 20 and outflow cannula 40 is provided as a pre-assembled unit.The surgeon gains access to the heart, preferably using a left subcostalor left thoracotomy incision exposing the left ventricular apex. Apledgeted purse string suture is then applied to the epicardiumcircumferentially over the pump insertion site. A slit incision or anincision in the form of a cross or X, commonly referred to as a “crux”incision, is made through the apex of the heart into the interior of theleft ventricle using a cutting instrument such as a scalpel. Pump 20,member 60, and outflow cannula 40 are then inserted through the cruxincision or slit incision and positioned within the left ventricle sothat cannula 40 extends through the aortic valve into the aorta and aninlet opening of inlet element 21 of pump 20 is positioned within theleft ventricle. Ring 80 is positioned on the outside of the heart asdepicted in FIG. 4. Proper placement of the components can be verifiedby fluoroscope or other imaging technique. After placement, the pump canbe started by applying electrical power from the external or implantablepower source, and proper outflow may be verified using echocardiography.After outflow is verified, crux incision is closed around member 60, asby suturing, and ring 80 is secured to the exterior of the cardiac wall.It should be noted that the ring 80 may alternately be mounted to theheart prior to performing the incision.

As shown in FIG. 4, in the implanted condition, ring 80 is mountedadjacent the apex of the subject's heart. Ring 80 and pump 20 areconnected to elongate member 60 remote from one another so that rigidelongate member 60 maintains pump 20 in position relative to ring 80.This maintains the pump and outflow cannula 40 in position relative tothe heart.

The aortic valve is one of the atrioventricular valves of the heart. Itlies between the left ventricle and the aorta. The ascending aorta 108is a portion of the aorta commencing at the upper part of the base ofthe left ventricle. The aortic arch 110 also known as the transverseaorta begins at the level of the upper border of the second sternocostalarticulation of the right side, and runs at first upward, backward, andto the left in front of the trachea. It is then directed backward on theleft side of the trachea and finally passes downward on the left side ofthe body of the fourth thoracic vertebra, at the lower border of whichit becomes continuous with the descending aorta 112.

When the device is in the implanted condition shown in FIG. 9, theoutflow cannula 40 projects through the aortic valve into the ascendingaorta, but preferably terminates proximal to the arch 110 of the aorta.Thus, tip 70 of cannula 40 is preferably disposed distal to the aorticvalve of the subject's heart, but the distal extremity of the tip isproximal to the aortic arch. This position of the outflow cannula 40 isadvantageous in that it minimizes contact between the outflow cannulaand the walls of the aorta, and thus minimizes trauma andthrombogenesis. The secure positioning of the pump 20 and outflowcannula 40 relative to the heart, provided by ring 80 and member 60,help to allow positioning of the cannula tip just distal to the aorticvalve. Because the device is securely held in place within the heart,there is little or no possibility that movement of the cannula relativeto the heart will allow the tip to move proximally, into the ventricle.

In the implanted or operative condition, the axis 19 of the pump extendsnear the apex of the heart, and the inlet opening of the inlet element21 of the pump 20 is disposed inside the left ventricle and is aimedgenerally in the direction toward the apex of the heart. The length ofelongate member 60 is such that the inlet 21 of pump 20 is remote fromthe aortic valve. This position and orientation provide certainadvantages. Fibrous structures of the aortic valve, just proximal to theopening of the valve, do not get sucked into the inlet of pump 20.Moreover, the inlet 21 of the pump 20 will preferably not be occluded bythe ventricular wall or the interventricular septum of the heart.However, occlusion of the inlet 21 by the ventricular wall or septum maystill be possible, particularly in certain patient populations. Inaddition, a suction condition may still occur.

Certain modifications or additions to VAD 10 may help ensure that heartstructures do not get sucked into the pump inlet and that suctionconditions do not occur. For example, FIG. 5 illustrates a VAD 115similar to VAD 10 with certain modifications. VAD 115 may include foursections including a pump 120, an outflow cannula 140, a rigid elongatemember 160, and an anchoring element 180. Pump 120 and outflow cannula140, as well as outflow cannula tip 170, may be identical to pump 20,outflow cannula 40, and outflow cannula tip 70, described in connectionwith VAD 10. Rigid elongate member 160 may be similar to rigid elongatemember 60, with one difference being how rigid elongate member 60couples to anchor element 180.

Anchor element 180 is illustrated in greater detail in FIG. 7.Generally, anchor element 180 may include a body 182, illustrated as asubstantially cylindrical member in FIG. 7. The body 182 may define afirst channel 184 and a second channel 188. The second channel 188 mayserve to facilitate coupling rigid elongate member 160 to the anchorelement 180, as well as to allow electric wiring 167 to pass from insiderigid elongate member 160 to fitting 200. The function of, andadditional structure related to, first channel 184 is described ingreater detail below.

Anchor element 180 may also include a ring 192 coupled to body 182 via aspherical element 190. The body 182 may have a length that issubstantially greater than the thickness of the ring 192. For example,the length of body 182 may be between about 25 mm and 45 mm, betweenabout 30 mm and 40 mm, or about 35 mm. The thickness of ring 192 may besubstantially less than the length of the body 182, and may be, forexample, between about 1 mm and 5 mm. It should be understood that thesedimensions are merely exemplary and are not intended to limit the scopeof the invention. With this configuration, ring 192 and sphericalelement 190 may slide up or down body 182 when in an unlocked condition,with the ring 192 and spherical element 190 being translationally androtationally fixed when in a locked condition. The ring 192 may havegenerally similar structure as ring 80 of VAD 10 and serve a similarfunction. In other words, during implantation of VAD 115, ring 192 maybe mounted to the heart, for example at the apex, to secure anchorelement 180 thereto. Spherical element 192 may provide an amount ofpolyaxial relative motion between body 182 and ring 192 to allow forslight movement of pump 120 via its connection to rigid elongate member160.

A method of implantation of VAD 115 may be generally similar to themethod of implantation of VAD 10 described above. For example, aftergaining access to the heart, VAD 115 may be inserted into the heartthrough a crux incision through the apex of the heart. As illustrated inFIG. 8, pump 120, elongate member 160, and outflow cannula 140 may beinserted through the crux incision and positioned within the leftventricle so that cannula 140 extends through the aortic valve into theaorta with an inlet opening of inlet element 121 of pump 120 positionedwithin the left ventricle. Prior to securing ring 192 to the apex of theheart, the distance which the VAD 115 extends into the heart may beprecisely controlled by changing the distance which the body 182 ofanchor element 180 extends into the apex of the heart when the body 182is in the unlocked condition with respect to ring 192. Once the positionof the VAD 115 is suitable, the body 182 and ring 192 may betransitioned into the locked condition to prevent translation of thebody 182 with respect to the ring 192, and the ring may be mounted tothe heart, for example with sutures.

Once mounted to the heart, the surgeon may utilize first channel 184 ofbody 182 to perform further procedures in the heart, if desired. Forexample, as shown in FIG. 9, the surgeon may pass a catheter 300 throughfirst channel 184, including passing the catheter 300 through one-wayvalve 185 within first channel 184. One-way valve 185 may prevent fluidfrom exiting the heart through first channel 184 while allowing items tobe passed through the channel. For example, valve 185 may be a duckbillvalve formed of a resilient material that generally conforms to objectsinserted therethrough, providing a fluid tight seal before, during, andafter insertion of items through first channel 184. It should beunderstood that other types of one-way valves may be used as analternative to a resilient duckbill valve.

In one example, catheter 300 may include one or more inner chambershousing one or more components to be passed through anchor element 180.For example, catheter 300 may house an expandable stent 400 while thestent is in a collapsed condition having a relatively small sizecompared to the expanded condition. Once at least a portion of the stent400 is passed through the first channel 184 via the catheter 300, thecatheter 300 may be removed or the stent 400 may otherwise be releasedof the catheter 300 constraining the stent 400. Once the constraint isat least partially removed, stent 400 may transition from the collapsedcondition to the expanded condition, for example as illustrated in FIG.10. The stent 400 may be formed of a superelastic shape-memory alloy,such as Nitinol, or any other suitable expandable and collapsiblematerial. Preferably, stent 400 is self-expandable so that, in theabsence of applied force, the stent 400 tends to take a particularpre-set shape which may be set, for example, by heat setting. However,other types of stents, such as balloon expandable stents, may besuitable. For balloon expandable stents, an expandable balloon may beinserted along with a stent surrounding the balloon, with fluid beingpumped into the balloon to expand both the balloon and the stent asdesired.

Referring still to FIG. 10, the illustrated stent 400 includes aplurality of struts or splines. In particular, the illustratedembodiment includes four struts 410, each strut having an inner enddisposed adjacent the inner ends of the other spines and outer endsdisposed away from one another when the stent is in the expandedcondition. The stent 400 may also include a securing portion 420 tosecure the stent 400 to a mounting portion of the VAD 115. Asillustrated, securing portion 420 of stent 400 is mounted to anchorelement 180. Mounting may be accomplished, for example, via a frictionfit between the securing portion 420 of stent 400 and a portion of theanchor element 180, such as the one-way valve 185. Alternatively, otherstructures may be provided on anchoring element 180, such as clips orretainers, to secure the stent 400. Still further, if a portion of stent400 extends completely through first channel 184 and outside the heart,other methods such as suturing an end of the stent 400 to the anchoringelement 180 may be performed as desired. It should be noted that othercomponents of VAD 115 may serve as the mounting portion for stent 400.For example, stent 400 may be secured to the rigid elongate member 160and/or a portion of inlet element 121. Still further, it is not strictlynecessary for the stent 400 to be mounted to the VAD 115 at all, as longas the stent 400 is secured within the heart. For example, if componentsof stent 400 are in direct contact with portions of the heart, such asthe heart walls, the stent 400 may provide enough radial force to remainsubstantially stationary without needing to be mounted to the VAD 115.

Proper placement of the VAD 115 and stent 400 may be verified byfluoroscope or other imaging technique. Once proper positioning isconfirmed, the surgeon may insert a secondary sealing element into firstchannel 184, such as a screw or a resilient plug. The secondary sealingmember may act as a backup fluid-tight seal to ensure that, in the eventone-way valve 185 loses its fluid-tight seal, the first channel 184remains fluid-tight. One example of possible positioning of thecomponents is illustrated in FIG. 11. As shown here, VAD 115 ispositioned with tip 710 on the outflow side of the aortic valve, pump120 and stent 400 within the left ventricle, and ring 192 of anchorelement 180 adjacent the apex of the heart. One or more of the struts410 of stent 400 may be in contact with and/or adjacent papillarymuscles PM, chordae tendinae CT, walls of the heart, theinterventricular septum IVS, or other heart structures.

After placement, the pump can be started by applying electrical powerfrom the external or implantable power source, and proper outflow may beverified using echocardiography. After outflow is verified, the cruxincision may be closed and the ring 192 secured to the exterior of thecardiac wall. It should be noted that ring 192 may be secured to theheart initially so that the implant process is undertaken with the ring192 mounted to the heart. Once power is applied and the VAD 115 is in anoperating condition, blood is drawn into the inlet opening of inletelement 121, moved through pump 120, and returned to the aorta throughthe tip 170 of the outlet cannula 140, as indicated by the arrows inFIG. 11. However, as noted above, the low intraventricular pressurecaused by the pump 120 drawing blood into the inlet 121 creates thepotential for heart anatomy to be sucked into the inlet opening of inletelement 121. As shown in FIG. 11, the struts 410 of stent 400 may act toprovide a physical barrier to keep the anatomy, such as theinterventricular septum IVS or the ventricle wall, from being able toenter the inlet opening of the inlet element 121. The struts 410 may bein direct contact with the anatomy, providing resistance to the pressuregradient pulling the heart structure toward the inlet 121.Alternatively, the struts 410 may be adjacent the heart structure, suchthat if the heart structure begins to get pulled toward the inlet 121,the struts 410 provide a barrier to the heart structures being pulled infurther. It may be preferable to keep the struts 410 adjacent to, ratherthan in contact with, the heart structures during normal operatingconditions so that they do not otherwise interfere with normal operationof the heart and VAD 115. The stent 400 may also similarly function toprevent tissue from being pulled into the inlet opening of inlet element121 if the ventricle has relatively little fluid that would lead to asuction condition in the absence of stent 400.

Although stent 400 is described above as having four struts 410 withinner ends adjacent one another and outer ends spaced apart from oneanother, the stent 400 may take other suitable forms. For example, astent similar to stent 400 may be used with any number of struts,including one, two, three, or more than four struts. Further, analternative stent may take various shapes including circular,cylindrical, or conical when in the expanded condition. Such alternativestents may be laser cut from a single tube of material, for example froma cylinder of Nitinol, or may be formed by braiding material into amesh. For example, a stent 500 cut from a tube of Nitinol taking thegeneral shape of a cylinder in the expanded condition is illustrated inFIG. 12. Any shape stent that provides a barrier from heart tissueentering the inlet opening of inlet element 121 may be suitable. Asnoted with stent 400, such stents may be mounted to any portion of VAD115, such as the anchor element 180, the pump 122, the rigid elongatemember 160, or may not be mounted to the VAD 115 at all.

Further, although the use of a stent is described above with respect toone particular VAD 115, it should be understood that the conceptsdescribed herein may be applied to any heart pump that includes an inletelement defining an inlet opening positioned within a chamber of theheart. For example, FIG. 13 illustrates a different type of VAD 610.Briefly, VAD 610 includes and inlet element 621 having an inlet opening.VAD 610 also includes an outlet port 623. The outlet port 623 may beconnected to an outlet cannula, such as a flexible tube 624, thatconnects to the ascending aorta 108, for example, as shown in FIG. 14.Electrical wiring 667 may operably couple the pump housing 622 to apower source and/or controller 668 which may, for example, be positionedoutside the body of the patient. As best illustrated in FIG. 14, VAD 610may be coupled to the heart so that the pump housing 622 is positionedoutside the heart near the apex, with the inlet element 621 being theonly portion of the VAD 610 that extends into the ventricle. In thisembodiment, a stent such as stent 500 may be mounted to the inletelement 621 and expanded following implantation of the VAD 610 toprovide similar function as stent 400. Although not identified, pumphousing 622 may include a sealable channel to allow introduction ofstent 500 in a collapsed condition through the VAD 610, with the channelbeing sealed after introduction, expansion, and proper positioning ofthe stent to ensure the VAD 610 is fluid-tight. As illustrated, stent500 may be mounted to VAD 610 at least partially upstream of inletelement 621, although stent 500 may alternatively be constrained withinthe ventricle under its own radial force without the need to mount thestent 500 to the VAD 610. Alternately, the stent may be introduced intothe heart prior to the insertion of the inlet element 621 into theheart. In this case, the stent would first expand in the heart and theinlet element 621 would be inserted through the heart and through theinner diameter of the stent. The stent and the inlet element 621 may beprovided with mating structures, such as hooks, catches, or otherstructures, so that inlet element 621 may physically couple to the stentto keep the stent in place. However, such mating structures areoptional.

FIG. 15 illustrates a highly schematic VAD 710 implanted within the leftventricle LV. In this embodiment, VAD 710 includes a pump housing 722remote from the left ventricle. An inlet cannula is connected to thepump housing 722 with an inlet element 721 having an inlet openingpositioned within the left ventricle. The inlet element 721 may be aflexible tube, for example, extending through the apex of the heart andmounted thereto. Similarly, VAD 710 may include an outlet cannula 723extending from the pump housing 722 extending and mounted to theascending aorta 723. The outlet cannula 723 may also take the form of aflexible tube. A stent, such as stent 500, may be positioned at leastpartially upstream of the inlet element 721. As in other embodiments,the stent 500 may optionally be mounted to the VAD 710 near the inletelement 121. The stent 500 may be inserted into the left ventricle LValong with, or separately from, inlet element 721, as desired.

As should be clear from the embodiments described above, any VAD havingan inlet element with an inlet opening positioned within a ventricle maybe used in conjunction with a stent to provide the desired protectionfrom heart structure entering or otherwise interfering with bloodflowing into the VAD. As such, the concepts described herein apply toVADs with pumps inside the heart, outside the heart, or mounted to theheart, as well as VADs with outlet cannulas within the heart or remotefrom the heart.

Although the invention herein has been described with reference toparticular embodiments, it is to be understood that these embodimentsare merely illustrative of the principles and applications of thepresent invention. It is therefore to be understood that numerousmodifications may be made to the illustrative embodiments and that otherarrangements may be devised without departing from the spirit and scopeof the present invention as defined by the appended claims. For example,features of any one embodiment described above may be combined withfeatures of other embodiments described above without departing from thescope of the invention.

The invention claimed is:
 1. A ventricular assist system comprising: aventricular assist device including a pump and an inlet element definingan inlet opening, the inlet opening configured to communicate with thepump, the inlet element being adapted for positioning with the inletopening disposed within a ventricle of a heart when the system is in anoperative condition; an expandable stent adapted for positioning withinthe ventricle when the system is in the operative condition, the stentincluding a collapsed condition; a mounting operably coupled to thepump, the mounting defining a fluid channel configured to extend from afirst end outside the ventricle to a second end inside the ventricle,the fluid channel being fluidly sealed between a portion of the firstend and the second end so that fluid is prevented from passing from thesecond end of the fluid channel to outside of the first end of the fluidchannel; and a one-way valve positioned within the fluid channel anddefining an opening through the fluid channel, the stent having a firstposition including the stent passing through the one-way valve in thecollapsed condition.
 2. The system of claim 1, wherein the mounting isconfigured to secure a part of the stent in position relative to theinlet element when the stent is positioned within the ventricle.
 3. Thesystem of claim 2, wherein the mounting includes an anchor elementconfigured for attachment to the heart and the inlet element and thestent are configured to be secured to the anchor element when the systemis in the operative condition.
 4. The system of claim 3, wherein thefluid channel extends through the anchor element.
 5. The system of claim4, wherein the fluid channel has a diameter and the stent has thecollapsed condition and an expanded condition, the diameter of thechannel being adapted to allow the stent to pass through the fluidchannel when the stent is in the collapsed condition.
 6. The system ofclaim 5, wherein the anchor element includes a ring.
 7. The system ofclaim 5, wherein the mounting includes a substantially cylindricalmember configured to be mounted to the heart at various positions alonga length of the substantially cylindrical member.
 8. The system of claim1, further comprising a sealing element configured to be positionedwithin the fluid channel proximal to the one-way valve to seal the fluidchannel.
 9. The system of claim 1, wherein the stent includes aplurality of struts, each of the plurality of struts having an inner endand an outer end, the inner ends being disposed adjacent one another andthe outer ends extending away from one another when the stent is in anexpanded condition.
 10. The system of claim 1, wherein the stent has thecollapsed condition and an expanded condition, the stent beingsubstantially cylindrical when in the expanded condition.
 11. The systemof claim 1, wherein the stent is formed of a braided mesh.
 12. A methodof installing a ventricular assist device in a subject comprising, themethod comprising: implanting the ventricular assist device to thesubject so that an inlet opening of an inlet element is disposed withina ventricle of the heart and the inlet opening communicates with a pump;positioning an outflow cannula so that the outflow cannula communicateswith the pump and with an artery; positioning a stent in the ventricleat least partially upstream of the inlet opening; positioning a mountingon a proximal end of the device so that the mounting and a channelwithin the mounting extend across a wall of the ventricle, the channelbeing fluidly sealed so that fluid is prevented from passing from insidethe ventricle to outside the ventricle through the channel; and passingthe stent through a one-way valve positioned at least partially withinthe channel of the mounting while the stent is in a collapsed condition.13. The method as claimed in claim 12, further comprising operating thepump to draw blood from the ventricle and return the blood to the arterythrough a heart valve and holding a wall of the ventricle away from theinlet opening with the stent.
 14. The method of claim 12, furthercomprising transitioning the stent from the collapsed condition to anexpanded condition.
 15. The method of claim 12, further comprisingsealing the channel with a sealing element.